Many machines include one or more components that rotate relative to one another. For example, typical excavators, cranes, foundation drills, material handlers, etc. include a housing disposed on top of an undercarriage. The housing is attached to a work implement such as a bucket connected to an arm and/or a boom. The housing rotates about a vertical axis with respect to the undercarriage. These machines may include a positioning system that includes a motor that rotates a gear assembly associated with a swing gear train, which in turn, rotates the housing. A closed loop control system positions the housing to a desired position. An operator rotates the housing to a desired position by accelerating the housing from a start position and decelerating the housing prior to reaching the desired position. However, the inertial forces created by a rotating housing with varying loads make it difficult to rotate the housing to the desired position accurately. Specifically, once the machine begins a rotational motion, inertia caused by the rotation may cause the housing to overshoot the desired position. This problem is prevalent when the excavator is working on a hillside or when the work implement of the machine is carrying a full load.
Automated controls that regulate the dig and dump cycles of these machines require accurate sensors to monitor the actual position of the housing. Some machines include a position-sensing system with a sensor that generates a signal related to proximity of the sensor element to a component or to a projection of a component, such as a gear tooth. Other position-sensing systems may include a sensor that senses rotational movement of a component, such as a gear. Unfortunately, a number of factors may cause significant variations in the values of the signals generated by such sensors. For example, vibrations, temperature variations, variations in the characteristics of the sensor and/or variations in the characteristics of power supplied to the sensor may increase or decrease the sensor signal value. Because of variations in such parameters, a position-sensing system employing one or more sensors may be inaccurate and therefore more robust position-sensing systems are needed.